The present invention relates generally to a modular biopsy, ablation and delivery needle apparatus that allows a biopsy needle to be inserted into a delivery needle, and, absent the biopsy needle, allows an inner ablation needle to be introduced and engaged with the delivery needle to form a microwave antenna. The present invention also relates to methods for biopsying and ablating tumors and coagulating the insertion track using the modular apparatus.
In the U.S., the lifetime chance of developing an invasive cancer is 46% for men and 38% for women. Cancer is the second leading cause of death in the U.S. and is a major cause of death worldwide. In the U.S. in 1998, there were an estimated 564,800 deaths due to cancer with 1,228,600 new cases of invasive cancer diagnosed. Over 40% of the deaths are associated with primary and metastatic liver cancer.
Outside the U.S., primary liver cancer (hepatocellular carcinoma) accounts for one of the largest cancer-related mortalities in the world (about 1,250,000 per year) in adults. In Japan, liver cancer is the third most common cause of death in men.
Of the over 1 million newly diagnosed U.S. cancer patients each year, hundreds of thousands will develop liver cancer during the course of the disease. For liver metastases that result in or are associated with death, estimates vary but are conservatively estimated at more than 230,000 annually in the U.S. Numerous studies of colorectal carcinoma have shown that liver metastasis is the primary determinant of patient survival.
Patterns of metastasis can be explained in part by the architecture of the circulatory system. Cancers in the intestine and many other tissues often colonize the liver first because the liver contains the first downstream capillary bed. It is estimated that 131,600 new cases of colorectal cancer were detected in 1998 and that 98,000 of them will eventually have liver involvement. Due to a lack of treatment options and the likelihood of recurrence, the American Joint Committee on Cancer projects that less than 1% of the patients diagnosed with nonresectable liver metastasis will be alive in 5 years.
Unfortunately, except for the small number of patients who have a form of cancer that can be surgically resected, there is no effective treatment. Therapies for nonresectable tumors include chemotherapy, radiation, transcatheter arterial embolization, chemoembolization and cryotherapy. Of particular interest are the percutaneous ablative techniques using ethanol, acetic acid, hot saline solution, laser, radiofrequency (RF), microwave, gene therapy and focused ultrasound.
Recent improvements in computed tomography (CT), ultrasound imaging and magnetic resonance imaging (MRI) have enabled physicians to detect tumors at an earlier stage and to locate them more precisely. These improvements have increased the use of laparoscopic and percutaneous procedures. As a result, RF, microwave, and cyroprobe devices have been developed to be used in the treatment of preselected sites. A number of problems exist with respect to these currently available devices. For example, cyroprobes generally require laparotomy because of their relatively large diameter, precluding a simpler, less traumatic approach. RF ablation relies on electrical conduction to deliver energy to tissues away from an RF ablation electrode. As tissue adjacent to the RF ablation electrode becomes desiccated or charred, the impedance increases, thereby limiting conduction through the desiccated or charred tissue. In addition, scar tissue, blood vessels or other tissue inhomogeneity within the ablation site may alter the conduction path of the RF current. Microwave coagulation therapy (MCT), however, destroys the diseased tissue though propagation of electromagnetic waves from a microwave antenna. Because the energy is deposited into the tissue away from the antenna without relying solely on conduction currents, little or no charring occurs with microwave coagulation therapy as compared to RF ablation methods. Furthermore, any charring that might occur does not affect energy deposition patterns to the extent that it would for RF ablation methods because energy can be propagated beyond any charred tissue since conduction through the charred tissue is not required. Therefore, microwave antennas can ablate tissue with little or no charring and with little or no alteration of their energy deposition patterns (typically measured by a specific absorption rate (SAR)) by tissue inhomogeneities. Despite the advantages offered by MCT, a need in the art exists for small-diameter microwave antennas that can precisely follow the biopsy needle track.
This need in the art is particularly acute in liver surgery. For instance, excessive bleeding and bile leakage during surgical procedures within the liver are common. Not surprisingly, large instruments are more traumatic than smaller ones. Furthermore, attempts at biopsy and thermotherapy of tumors can result in seeding of the carcinoma along the track during instrument removal and additional bleeding along the track. Localizing the tumor site can also be a problem and can result in additional trauma and bleeding, for instance, when a biopsy tool is used to sample and localize the tumor and subsequently the thermotherapy device is reinserted to treat the tumor.
Accordingly, there is a need for a small diameter delivery device that can facilitate the biopsy and ablation of a tumor through a single protected puncture site without the need to withdraw the device from the puncture site during biopsying and ablation. Further, there is a need for a device that can efficiently ablate the track during removal to reduce bleeding and the chances of track seeding.
The present invention is directed to a modular biopsy and microwave ablation needle and delivery apparatus adapted for in situ assembly, biopsy and ablation of tumors in tissues, and ablation of the track upon removal of the apparatus. More particularly the apparatus is adapted to the biopsy and ablation of tumors in solid organs that have a propensity to bleed, for instance, the liver. The present invention also relates to methods for the biopsy and ablation of tumors using the modular biopsy and microwave ablation needle and delivery apparatus.
Generally, a modular needle apparatus for performing biopsy and ablation of tissue abnormalities through a puncture site comprises an elongated hollow delivery needle, a biopsy needle, and an ablation needle. The hollow delivery needle extends longitudinally a first predetermined distance from an open proximal end to an open distal end, with a lumen extending therebetween. The lumen may accommodate either the biopsy needle or the ablation needle inserted through the open proximal end. The distal end of the delivery needle may be sharpened to pierce tissue. Alternatively or additionally, an obturator may be inserted within the lumen of the delivery needle to stiffen the delivery needle and provide a sharp tip to facilitate piercing tissue. As yet another alternative, the biopsy needle acts as the obturator of the delivery needle, and the biopsy needle and delivery needle are inserted into tissue as a unit. In that case, the biopsy needle itself serves to stiffen the assembly and provide a sharp point for piercing tissue. The biopsy needle may be of any type known in the art and may comprise a single piece, two pieces, or more.
Both the biopsy needle and the ablation needle are longer than the first predetermined distance such that when either the biopsy needle or the ablation needle is inserted into the proximal port and distally displaced within the lumen of the delivery needle, a distal projection of either the biopsy needle or the ablation needle may extend beyond the distal end of the delivery needle. The distal projection of the ablation needle is adapted to form a microwave antenna. The microwave antenna may comprise one of many forms known in the art, for example, a monopole, a dipole or a helical coil antenna.
In a preferred embodiment, the delivery needle has a first connector adapted to connect to a second connector of the ablation needle when the ablation needle is inserted within the lumen of delivery needle. The ablation needle comprises a center conductor at least partially surrounded by a dielectric material, and the delivery needle comprises a conducting material wherein the combination of the delivery needle, the dielectric material and the center conductor comprise a coaxial transmission line when the first and second connectors are connected. The delivery needle thus comprises the outer conductor of the coaxial transmission line and the inner conductor of the ablation needle comprises the inner conductor of the coaxial transmission line. The ablation needle extends longitudinally a second predetermined distance from the second connector wherein the second predetermined distance is greater than the first predetermined distance whereby the ablation needle forms the distal projection extending beyond the distal end of the delivery needle when the first and second connectors are connected. The distal projection of the ablation needle forms the microwave antenna that is coupled to the coaxial transmission line.
In another embodiment of the invention, the delivery needle and the ablation needle are not adapted to form a transmission line. Instead, the transmission line is contained within the ablation needle. The delivery needle extends longitudinally a first predetermined distance from an open proximal end to an open distal end, with a lumen extending therebetween as described generally above. The ablation needle extends longitudinally a third predetermined distance from a distal end wherein the third predetermined distance is greater than the first predetermined distance whereby the ablation needle forms a distal projection extending beyond the distal end of the delivery needle when the ablation needle is distally displaced within the lumen of the delivery needle. The distal projection of the ablation needle forms the microwave antenna. The remainder of the ablation needle comprises a transmission line that couples to the microwave antenna. The microwave antenna may be a dipole, a monopole or a helical coil antenna.
For the embodiments described herein, the biopsy needle, which may be an aspirating or a coring type, extends distally from its proximal end a fourth predetermined distance wherein the fourth predetermined distance is greater than the first predetermined distance. The biopsy needle may comprise a cannula and a stylet adapted to be disposed within the cannula. The stylet may include a matched point wherein the matched point matches a distal end of the cannula.
Methods of ablating tissue are also described. First, an ablation system as described herein is provided. Then, the distal end of the delivery needle is introduced into a tissue sample in a predetermined area. Next, the distal end of the ablating needle is inserted into the lumen of the delivery needle through the open proximal end, and the ablating needle is then advanced until the first and second connectors are adjacent one another. Next, the first and second connectors are connected. Then, a coaxial connector of the modular needle apparatus is electrically coupled to a coaxial connector of the microwave energy source. Microwave energy may then be delivered to the microwave antenna, thus ablating the tissue abnormality in the predetermined area. In other embodiments, the steps of inserting a biopsy needle into the delivery needle, biopsying the tissue and removing the biopsy needle with a tissue sample precede or follow the step of inserting the ablation needle.
Withdrawing the ablation needle from the tissue sample after the ablation of the tissue abnormality has been performed leaves an insertion track. The ablation needle may xe2x80x9cseedxe2x80x9d diseased cells within the insertion track as the ablation needle is withdrawn. The present invention is directed towards devices and methods to ablate the insertion track, thereby killing any diseased cells within the insertion track. In addition, track ablation minimizes bleeding, and, if performed within the liver, stems bile leakage. To minimize the damage to healthy tissue, the insertion track should be ablated with minimal overlap between adjacent ablations. Thus, the modular needle apparatus preferably has a plurality of first markings on its surface wherein the plurality of first markings are spaced apart a distance approximately equal to an effective antenna length of the microwave antenna. After ablating the tissue abnormality, a clinician may partially withdraw the ablation needle from the insertion track approximately an effective antenna length as gauged by observing the plurality of first markings. The clinician may then perform an ablation of the insertion track. The steps of partially withdrawing and ablating the insertion track may be repeated as required to complete the track ablation. To aid the determination of whether the track ablation has been completed, the modular needle apparatus preferably further comprises a second marking adjacent a proximal edge of an antenna radiation pattern of the microwave antenna. In such an embodiment, the steps of partially withdrawing the modular needle apparatus and ablating the insertion track are repeated until a partial withdrawing of the modular needle apparatus positions the second marking adjacent an edge of an organ containing the tissue abnormality. At this point, the partial withdrawing step is stopped and a final ablation of the insertion track performed. Note that although the plurality of first markings and the second markings are described with respect to the delivery needle of the present invention, these markings may be applied to any suitable interstitial ablation device.
Because only a small area surrounding the insertion track need be ablated to prevent seeding, bleeding and (if applicable) bile leakage, the clinician may decrease the diameter of the field of the antenna and/or lengthen the field to speed track ablation time. Such changes in the field will also minimize damage to healthy tissue surrounding the insertion track.
It is to be noted that the plurality of first markings and the second marking and methods of using the same may be applied to other interstitial thermotherapy devices such as RF ablation devices or cryoprobes. In these embodiments, the plurality of first markings would be spaced apart an xe2x80x9ceffective ablationxe2x80x9d length which is defined analogously to the effective antenna length. The effective ablation length thus represents the extent of effectively ablated tissue after performing an ablation with the interstitial thermotherapy device.
Additional objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.